Inverted magnetic isolator

ABSTRACT

A current determiner comprising a first input conductor and a first current sensor, formed of a plurality of magnetoresistive, anisotropic, ferromagnetic thin-film layers at least two of which are separated from one another by a nonmagnetic layer positioned therebetween, and both supported on a substrate adjacent to and spaced apart from one another so they are electrically isolated with the first current sensor positioned in those magnetic fields arising from any input currents. A first shield/concentrator of a material exhibiting a substantial magnetic permeability is positioned between the substrate and the first input conductor. The substrate can include a monolithic integrated circuit structure containing electronic circuit components of which at least one is electrically connected to the first input conductor. A similar second current sensor can be individually formed, but can also be in the current determiner structure that is supported on the substrate along with a second input conductor supported on the substrate suited for conducting input currents therethrough. This second input conductor is positioned at that side of the second current sensor opposite to that side thereof facing the substrate so as to be adjacent to, yet spaced apart from, the second current sensor to thereby be electrically isolated from any direct circuit interconnection therewith on the substrate but to have the second current sensor positioned in those magnetic fields arising from the input currents in the second input conductor. In addition, a second shield/concentrator layer of material exhibiting a substantial magnetic permeability to serve as a magnetic field concentrator is positioned at that side of the second input conductor opposite to that side thereof facing the substrate. In the first instance, the second shield/concentrator layer is electrically connected to the second input conductor, and can be so connected in the second instance.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Provisional Application No.60/610,700 filed on Sep. 17, 2004 for “INVERTED MAGNETIC ISOLATOR”.

BACKGROUND OF THE INVENTION

The present invention relates to ferromagnetic thin-film structuresexhibiting relatively large magnetoresistive characteristics and, moreparticularly, to such structures used to magnetically couple signalsfrom a source to an isolated receiver.

Many kinds of electronic systems make use of magnetic devices includingboth digital systems, such as memories, and analog systems such as fieldsensors. Magnetometers and other magnetic sensing devices are usedextensively in many kinds of systems including magnetic disk memoriesand magnetic tape storage systems of various kinds. Such devices provideoutput signals representing the magnetic field sensed thereby in avariety of situations.

One use for such magnetic field sensors is the sensing of magneticfields generated by electrical currents in a conductor as a basis forinferring the nature of such current giving rise to these fields. Whilethis has long been done for magnetic fields generated by substantialcurrents, such sensing becomes more difficult to accomplish in smallerranges of currents that include relatively quite small currents. Theneed for sensing fields due to such small currents arises, for instance,in situations where the currents generating the fields to be measuredare provided merely as a basis for conveying signal information ratherthan for transmitting substantial electrical energy.

Such a situation occurs in many medical systems, instrumentation systemsand control systems where there is often a need to communicate signalsto system portions over signal interconnections from an external sourceor from another portion of the system. Often, the conductors carryingsignal currents for such purposes must be electrically isolated from theportion of the system containing the sensor arrangement for thosesignals to measure the resulting magnetic fields. As an example, a longcurrent loop carrying signal information in the loop current may,because of resistances occurring in ground path interconnections usuallyconsidered as resistance free, become subject to having large voltagepotentials relative to some ground point developed thereon. Suchpotentials must in many instances be kept from the signal sensing andreceiving circuitry to avoid damage thereto even though that circuitrymust still be able to capture the signal information contained in theloop current.

Signal isolators for these purposes are often preferably formed inmonolithic integrated circuit chips for reasons of cost, convenience andsystem performance. In such an arrangement, one or more solid statemagnetic field sensors are used to detect the magnetic fields providedby the currents containing the signals. A kind of magnetic field sensorwhich has been used in this situation is a Hall effect device. Suchdevices are often not satisfactory for sensing the magnetic fields dueto small currents because of the limited sensitivity they exhibit withrespect to magnetic fields.

Furthermore, there is often a lack of satisfactory remedial orsupplementary measures in such arrangements for improving the limitedsensitivity of Hall effect devices. The use of field concentrators isdifficult to provide in a monolithic integrated circuit containing aHall device because of the magnetically sensitive axis of that devicebeing perpendicular to the directions the Hall device in the monolithicintegrated circuit extends over the substrate supporting that device,i.e. the device axis of sensitivity is parallel to the thickness of thedevice rather than to the width or length thereof. Also informationprovided by Hall devices as to the magnetic fields measured thereby isin the form of a voltage which limits the use of such devices in bridgecircuits which might otherwise be used for purposes of increasing theoutput signal providing the current signal information.

Another possibility in either hybrid integrated circuits or monolithicintegrated circuits for signal isolation is the use of a light sourcehaving its electromagnetic radiation intensities controlled by signalcurrents from a signal source. Such a light source is electricallyisolated from a light detector provided in the integrated circuit thatis used to infer the nature of the signal currents from the lighttransmitted to and received thereby. Difficult engineering and economicproblems make this an unsatisfactory solution as are various alternativecapacitance based coupling solutions because of the same kinds ofproblems.

A further possibility has emerged in these circumstances for signalisolation in both hybrid integrated circuits and monolithic integratedcircuits involving a current determiner comprising an input conductor,typically in some coiled configuration, and a current sensor bothsupported on a substrate adjacent to and spaced apart from one anotherso they are electrically isolated but with the current sensor positionedin those magnetic fields arising from any input currents in the inputconductor. Such an isolated signals current determiner is an attractivedevice for these purposes in being both rapid in operation andeconomical in cost.

In the recent past, providing such current sensors as magnetoresistiveeffect based sensors in the form of an intermediate thin layer of anelectrically conductive, nonmagnetic separating material having twomajor surfaces on each of which an anisotropic ferromagnetic thin-filmis positioned has been found to lead to a “giant magnetoresistiveeffect” in the sensor if the thicknesses of the ferromagnetic thin-filmsand the intermediate layers in such a “sandwich” structure have beenmade sufficiently small. This effect can be enhanced by forming suchsensors with additional alternating ones of these ferromagnetic filmsand intermediate layers to form superlattices. The resulting enhanced“giant magnetoresistive effect” can yield a magnetoresistive responsewhich can be in the range of up to an order of magnitude greater thanthat due to the well known anisotropic magnetoresistive response.

Such an isolated signal current determiner can be used to couple inputsignals provided in an input conductor to a receiver isolated from theinput conductor, the input signals then being substantially replicatedin a receiver circuit to provide similar representations of those inputsignals at the receiver output. This is often a satisfactory arrangementfor coupling digital data input signals into a system isolated from thesource of the input signals, and a high withstanding voltage can beprovided between the system input and output to achieve very substantialsignal isolation between them.

However, the input conductor is usually provided in the form of a planarcoil separated by electrical insulating material from the currentdeterminer below formed on a monolithic integrated circuit, serving as asubstrate while also providing the operating circuitry for the system,and eases the fabrication of the relatively thick, magneticallypermeable material layers serving as shields and field concentratorsthat must be provided on a side of the coil opposite that side thereofat which the current determiner is located. Thus, the coil must then befabricated after the insulating material is deposited and an inputsignal source must thereafter be connected to the planar coil requiringsubstantial bonding pads at the ends of the coil for suchinterconnections. Furthermore, the signal progresses in only onedirection in such a system thereby requiring two such systems forinteractive communication between the initial signal source and theinitial receiver. Thus, there is a need for a signal isolation deviceexhibiting relatively high sensitivity, relatively high powerefficiency, relatively high withstanding voltage and an interactivecapability, but which can be fabricated at a reasonably economic costwith good reliability.

BRIEF SUMMARY OF THE INVENTION

The present invention provides a current determiner having an output atwhich representations of input currents are provided for input currentsthat are supplied from a source, the current determiner comprising afirst input conductor and a first current sensor both supported on asubstrate adjacent to and spaced apart from one another so they areelectrically isolated with the first current sensor positioned in thosemagnetic fields arising from any input currents. A firstshield/concentrator of a material exhibiting a substantial magneticpermeability is positioned between the substrate and the first inputconductor. The first current sensor is formed of a plurality ofmagnetoresistive, anisotropic, ferromagnetic thin-film layers at leasttwo of which are separated from one another by a nonmagnetic layerpositioned therebetween. The first shield/concentrator layer cansupported on the substrate between the first input conductor and thatsubstrate, formed as a supporting structure in a current determinerhousing, or a shield structure attached to such a supporting structure.The substrate can include a monolithic integrated circuit structurecontaining electronic circuit components of which at least one iselectrically connected to the first input conductor.

A second current sensor can be individually formed, but can also be inthe current determiner structure that is supported on the substrate thatis also formed of a plurality of magnetoresistive, anisotropic,ferromagnetic thin-film layers at least two of which are separated fromone another by a nonmagnetic layer positioned therebetween along with asecond input conductor supported on the substrate suited for conductinginput currents therethrough. This second input conductor is positionedat that side of the second current sensor opposite to that side thereoffacing the substrate so as to be adjacent to, yet spaced apart from, thesecond current sensor to thereby be electrically isolated from anydirect circuit interconnection therewith on the substrate but to havethe second current sensor positioned in those magnetic fields arisingfrom the input currents in the second input conductor. In addition, asecond shield/concentrator layer of material exhibiting a substantialmagnetic permeability to serve as a magnetic field concentrator ispositioned at that side of the second input conductor opposite to thatside thereof facing the substrate. In the first instance, the secondshield/concentrator layer is electrically connected to the second inputconductor, and can be so connected in the second instance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a portion of a monolithic integrated circuitstructure embodying the present invention,

FIGS. 2A and 2B are layer diagrams of parts of the structure portionshown in FIG. 1,

FIG. 3 is a plan view of a portion of an alternate monolithic integratedcircuit structure embodying the present invention,

FIGS. 4A and 4B are alternative layer diagrams of parts of the structureportion shown in FIG. 3 as mounted,

FIG. 5 represents an approximation of a portion shown in the FIG. 2Alayer structure in a coordinate space,

FIG. 6 is a plan view of a portion of an alternate monolithic integratedcircuit structure embodying the present invention, and

FIGS. 7A and 7B are layer diagrams of parts of the structure portionshown in FIG. 6,

FIG. 8 is a plan view of a portion of an alternate monolithic integratedcircuit structure embodying the present invention, and

FIGS. 9A and 9B are layer diagrams of parts of the structure portionshown in FIG. 8,

FIG. 10 is a plan view of a portion of an alternate monolithicintegrated circuit structure embodying the present invention, and

FIG. 11 is a layer diagram of part of the structure portion shown inFIG. 10.

DETAILED DESCRIPTION

A basic “sandwich” structure magnetic field sensor has a sensorelectrical resistance versus applied external field characteristic foran external magnetic field applied in one direction perpendicular to itseasy axis that generally appears in its graph on a resistance versusfield Cartesian coordinates graph as a horizontal line at the sensorminimum resistance value except for an excursion therein to greaterresistance values located at or near to the zero applied magnetic fieldvalue. This excursion typically appears as a more or less “baseless”isosceles triangular shape with an increase from the minimum sensorresistance value to a peak sensor resistance value at zero fieldfollowed by a decrease to the minimum sensor resistance value, or it mayappear to be a triangular shaped excursion to higher resistance valuesexcept for a flat, or “plateau”, portion at the top thereof at themaximum sensor resistance value. Thus, plotting the characteristicsresulting from applying external magnetic fields in both directionsperpendicular to the sensor easy axis on the same graph results in apair of overlapping triangular excursion graphs approximately centeredabout the zero external applied field value as the basic “sandwich”structure current sensor resistance versus external fieldcharacteristic.

Such a characteristic has no sharp switching thresholds therein thusrequiring any such thresholds to be provided in the subsequentelectronic circuitry. In smaller sized sensors where the demagnetizationfields in the sensor magnetic layers become relatively more significant,the triangular shape shifts so as to provide a side more closelyparalleling the resistance axis of the graph to thereby result inproviding magnetic switching thresholds in the current sensor itself.Also, the double triangle characteristic described above for the basic“sandwich” structure field sensor is symmetrical on both sides of thezero value of externally applied fields.

Thus, some sort of a bias such as a bias magnetic field must be suppliedto such field sensors connected in sensor bridge circuits to force onepair of those sensors to operate on one side of their triangularcharacteristics and the other pair to operate on the other triangularside of their triangular characteristics if directions of appliedexternal magnetic fields are to be distinguishable. This asymmetryintroduced by the bias field makes possible the two pairs of thosesensors in such circuits changing their electrical resistances inopposite directions in the presence of an external applied field so asto make available a bridge circuit output signal. Such a bias fieldrequirement also limits the magnitudes of external applied fields to besensed to being less than the bias field magnitude for proper operation.Alternatively, a current bias could be introduced in the input conductorin which signal currents generate magnetic fields to be sensed by somecurrent sensors in a bridge circuit to set a reference point about whichinput current changes will result in corresponding output signalchanges. A further alternative is to just provide a field absolute valuesensor.

A “pinned” layer “sandwich” structure is provided by a “spin valve”structure in which one magnetic layer in a “sandwich” structure has itsmagnetization firmly maintained in a selected direction despitesignificant applied external magnetic fields while the other magneticlayer is relatively quite free to have its magnetization rotate inresponse to such applied external magnetic fields. This structureresults in a sensor electrical resistance versus applied external fieldcharacteristic for an external magnetic field applied in both directionsperpendicular to the sensor easy axis that generally appears shaped likea typical magnetic material hysteresis curve centered about a zero valueapplied field. This device electrical resistance versus external appliedfield hysteresis characteristic shown on a resistance versus fieldCartesian coordinates graph has two more or less parallel sidesapproximately centered about the zero external applied field value eachwith a substantial directional component paralleling the resistanceaxis. These sides extend between an upper saturation value at themaximum resistance value of the sensor and a lower saturation value atthe minimum resistance value of the sensor so that these sides representmagnetic switching thresholds leading to asymmetrical saturationresistance values on the opposite sides of the zero value of externallyapplied magnetic fields.

Because of this asymmetry in the sensor electrical resistance versusapplied external field characteristic, i.e. the upper saturation valueat the maximum resistance value of the sensor on one side of zero valueof externally applied magnetic fields and the lower saturation value atthe minimum resistance value of the sensor on the other, no biasmagnetic field or bias current is needed for such sensors in bridgecircuits. Changes in input current polarity in the input conductor willlead directly to changes in bridge output signal polarity.

The magnetic layer in the “pinned” layer “sandwich” structure having arelatively freely orientable magnetization is, as indicated, intended tobe magnetically more or less independent of the magnetic layer thereinhaving a relatively fixed orientation magnetization. The nonmagneticconducting layer is chosen to be relatively thick so that there isrelatively little exchange coupling between the two magnetic film layersin this structure, and there is also a relatively small magnetostaticcoupling therebetween. Although these characteristics can also be trueof a basic “sandwich” structure, they do not provide an asymmetry in theelectrical resistance versus applied external field characteristic forsuch structures.

Thus, going to a “spin valve” structure for the current sensor in thesignal isolator avoids the need for any biasing arrangement.Furthermore, the resulting bipolar output signal in a bridge can be usedto provide a doubling of the output signal magnitude range in responseto input digital data pulses.

In addition, the presence of an effective switching value hysteresis asa result of the current sensor resistance versus applied externalmagnetic field characteristic of the “spin valve” structure serves toeffectively filter out electrical noise accompanying the digital datacurrent pulses in the input signal provided to the signal isolator inputconductor or conductor coil. This comes about because the switching ofthe free magnetic layer in the current sensor “spin valve” structure,once it occurs, will not be undone by such noise due to this hysteresisrequiring a significantly different input conductor current value toagain switch the magnetization direction of that free layer from thevalue which previously switched that direction. Thus, the output fromthe current sensor is a “squared up” signal having relatively littlevariation from the normal logic value magnitudes expected therein ascompared to the digital data input signal applied to the inputconductor.

Of course, the maximum signal power can be extracted from the digitaldata input signal supplied to the isolator input conductor or conductorcoil by choosing that input conductor to have an effective impedancewhich matches the characteristic impedance of the input transmissionline connected thereto. Thus, the number of turns in the input conductorcoil, the length and the resistance of the individual loops in the coilcan be adjusted to have its characteristic impedance closely match thatof the incoming transmission line, although in some situations thesechoices must be supplemented by the use therewith of further structuresto provide such a match.

The digital data current pulses occurring in the input conductor orconductor coil after transmission thereto over a transmission line must,of course, have sufficient current magnitude to provide the necessarymagnetic fields thereabout to reach the saturation magnetizationmagnitudes of the “spin valve” current sensor. Thus, substantialelectrical power can be dissipated in transmitting such input digitaldata current pulse logic value signals over longer transmission lines.Such power requirements can be significantly further reduced byproviding, instead of pulses representing a binary bit by maintaining anessentially constant logic value current magnitude over the entire pulserate period, just an impulse-like current flow at the beginning of sucha pulse rate period in which such a logic value pulse is to occur. Thatis, a very short initial pulse in a pulse rate period can take the placeof a digital data current pulse lasting the entire pulse rate period tothereby significantly reduce the electrical power involved. The minimumduration of the impulse-like current pulse must exceed the rise time ofa magnetization orientation change in the “spin valve” current sensor tothe switching threshold, as increased by the loading of any parasiticcircuit components effective in the transmission of an input conductorpulse, to become a corresponding current sensor output signal pulse.

Also, in many situations, the signal isolator user will desire toprovide only typical logic signals that are generated in whatever logicsystem technology the user is employing at the logic signal generationsource to provide the basis for transmitting digital data on thetransmission line connected to the input of the signal isolator. Thatis, for instance, the signal source may be a monolithic integratedcircuit fabricated using complementary metal-oxide-semiconductor (CMOS)technology to result in that integrated circuit providing, at itsoutput, digital logic circuitry logic value voltage magnitudes common tothat technology. Since such logic signals typically will not havesufficient current or power capability to operate the input conductor orcoiled conductor of a signal isolator, a circuit must be provided aheadof that input conductor for converting logic value voltage magnitudes ina particular monolithic integrated circuit technology to currentmagnitudes sufficient to operate the input conductor.

Thus, an input signal converter will be convenient to provide at thesignal isolator input for both of these purposes. Such a converter willbe used to convert standard logic value voltage magnitude pulses forsome particular signal source technology to impulse-like current pulsesat the beginning of pulse rate periods to operate the input conductor orcoiled conductor of the signal isolator. This will free a user of thesignal isolator from any need to change the usual output digital logicsignals from the user's signal source in any way to meet the needs ofthat isolator, and frees that user from having to supply the powerneeded by the signal isolator to operate. Again, the input of thisconverter can be adjusted to have its characteristic impedance closelymatch that of the incoming transmission line including the use therewithof specific circuit structures to provide such a match.

Sequences of digital data logic value pulses can be converted tocorresponding impulse-like current excursions by submitting thosesequences of digital data logic value pulses to an analog differentiatorso that corresponding impulse-like voltage excursions of oppositepolarity occur at the differentiator output for both the leading edgeand the trailing edge of each such pulse. However, such differentiationof signals is inherently a noise generation process with that noisetypically increasing in magnitude as the pulse rate increases. Thus,substituting instead a very short duration pulse or impulse-like currentexcursion at the leading and trailing edges of each digital data logicvalue pulse approximates the differentiating process without generatingas much unwanted electrical noise.

Again, the minimum pulse width for these very short current pulses mustexceed the rise time of the magnetization orientation of the “spinvalve” current sensor to its rotational threshold value as increased byany parasitics involved with this circuit arrangement. Typically,assured switching with such short duration current pulses or excursionsrequires that the pulse amplitude be well beyond those necessary toprovide magnetic fields that just reach the saturation magnetizationmagnitudes of the “spin valve” current sensor. Nevertheless, because ofthe shortness of the current excursion duration, there will be adecrease in electrical power dissipated.

After such generation of current excursions in the input conductor orcoiled conductor of the signal isolator, recovering the correspondingdigital data from the isolator current sensor is determined in part atleast by the nature of the electrical resistance versus applied externalmagnetic field characteristic of that current sensor. As indicatedabove, this characteristic for a “spin valve” based “sandwich” structureappears as a hysteresis loop approximately centered on a zero appliedexternal field value, and having more or less parallel sides typicallyrepresenting magnetic saturation or switching thresholds extendingbetween the sensor minimum resistance value and maximum resistance valuewhich sides have a substantial directional component parallel to theresistance axis. The current sensor can be forced to one or the other ofthese extreme resistance value states by applying external magneticfields having magnitudes exceeding the magnitudes of the magneticsaturation or switching threshold values.

If the hysteresis characteristic parallel sides have the directionalcomponents thereof which are parallel to the resistance axis of thegraph also being relatively small, the primary direction of thehysteresis loop between the minimum and maximum resistance valuesappears canted with respect to the resistance value axis. As a result,the resistance value for the current sensor after the removal of anapplied external field will be either significantly less than themaximum resistance value for the current sensor or significantly morethan the minimum resistance value for that current sensor depending onapplied field direction. With sufficient canting, the sides of thehysteresis loop will approach one another to essentially merge into astraight line so that there will be a common resistance value after theremoval of an applied external field in either direction.

In this circumstance, a data latch needs to be used across the currentsensor output to provide “memory”, i.e. to retain the information as towhich of the extreme resistance value states last occurred in thecurrent sensor as a result of the occurrence of a short term currentpulse in the input conductor. That is, the occurrence in the currentsensor of a maximum resistance state value or a minimum resistance statevalue, corresponding to the largest output voltage signals from thecurrent sensor in response to a sense current or bridge operatingcurrent provided therethrough, will cause the data latch to go into oneof its logic states or the other. This logic state in the latch thusrepresents the information as to which extreme resistance value lastoccurred in the current sensor, and is information which could otherwisebe lost because of the final resistance value of the current sensor,after being in such a state followed by the corresponding magnetic fieldgenerated about the input conductor going to zero, being relativelysimilar subsequent to the sensor having been in either extremeresistance state. This closeness of the final resistance values of thesensor, upon the removal of any significant external magnetic fieldfollowing such a field having forced the sensor to either extremeresistance value state, occurs because of the canting of the hysteresisloop with respect to the resistance axis of the graph.

On the other hand, a resistance versus applied external fieldcharacteristic for a current sensor in the form of a hysteresis loophaving sides with directional components parallel to the resistance axisof the graph that are relatively large leaves the loop appearingrelatively “square”in that graph. In this situation, the current sensorhas final resistance values, upon the removal of any significantexternal magnetic field following such a field having forced the sensorto either extreme resistance value state, which are close in value tothe resistance value of the corresponding last extreme resistance valuestate which occurred in that sensor. In these circumstances, a datalatch is not needed across the current sensor output because the memoryof the last extreme resistance value state occurring in the currentsensor is effectively stored in that sensor by the final resistancevalue occurring in the sensor after removal of the applied externalmagnetic field. A sense current or bridge operating current providedthrough the sensor will result in corresponding output voltages for eachfinal resistance value sufficiently different from one another to berelatively easily distinguishable by the subsequent circuitry connectedto the sensor output.

Thus, there is a desire to obtain a hysteresis loop for a current sensorhaving a resistance versus applied external field characteristic in theform of a hysteresis loop which has the main extent thereof between thesensor maximum and minimum resistance value states extendingsubstantially parallel to the resistance axis to yield a “squared up”appearance. This requires that the externally applied magnetic field tobe sensed in the current sensor be oriented substantially parallel tothe easy axes of the magnetic material layers therein. Hence, the inputcurrent conductor, or the main extent of a coiled input currentconductor, is to be provided substantially perpendicular to the easyaxes of the magnetic layers in the current sensor. The resulting currentsensor will then “remember” the last extreme resistance value state towhich it was forced by external magnetic fields generated by currentexcursions in the input conductor or coiled input conductor in its finalresistance value occurring after the removal of such an externallyapplied magnetic field.

On the other hand, a current sensor having a resistance versus appliedexternal field characteristic in the form of a canted hysteresis loopalso is desirable even though added hysteresis has to be provided in theelectronic circuitry connected to the current sensor output. This isbecause magnetization direction reorientation is primarily accomplishedby rotational switching and only relatively limited magnetic fieldchanges are needed to do so. As a result, very rapid magnetizationdirection reversals occur, the current sensor devices can be compact,and lower power dissipation occurs in the input conductor. Such a looprequires that the externally applied magnetic field to be sensed in thecurrent sensor be oriented substantially perpendicular to the easy axesof the magnetic material layers therein. Thus, the input currentconductor, or the main extent of a coiled input current conductor, is tobe provided substantially parallel to the easy axes of the magneticlayers in the current sensor.

Signal isolators, based on the magnetoresistive sensing of correspondingmagnetic conditions generated therein by input signals delivered to itsinput, that are formed in accord with the foregoing structuralparameters can be advantageously fabricated using ferromagneticthin-film materials. Such devices may be provided on a surface of amonolithic integrated circuit to thereby allow providing convenientelectrical connections between the sensor device and the operatingcircuitry therefor, although they need not be so provided, as they canbe provided in hybrid integrated circuit arrangements too, or incombinations thereof. Those devices provided on a surface of amonolithic integrated circuit in the past have had the current sensorsfirst provided on that surface followed by providing electricalinsulating material and then the input conductor usually in the form ofa planar coil.

FIG. 1 shows a plan, or top, view of a part of a signal isolator chip inwhich the order of stacking these device structural components outwardlyfrom the substrate is reversed although, in this example, this isolatoris separately formed as a hybrid integrated circuit on an insulatingsubstrate, such as an electrical insulating layer covered silicon orceramic material substrate, rather than as a portion of a monolithicintegrated circuit so that the operating circuitry for the system willbe provided externally thereto. Alternatively, as will be shown in asubsequent example, the signal isolator can be formed as part of amonolithic integrated circuit including a supporting semiconductor chipas part of the isolator substrate which can have conveniently providedtherein the operating circuitry for that signal isolator. The outerprotective or passivation layer that is typically provided over thestructure shown in these figures in actual use has been omitted in thisview for clarity as have some other layers so that the thereby visiblestructure portions are shown in solid line form except for thosestructure portions beneath other structure portions appearing in thosefigures which are shown in dashed line form. A further exception is thatsome other structures have been indicated in outline only by furtheralternative dashed lines forms again for clarity to avoid having thesestructures cover over other underlying structures.

Corresponding to FIG. 1 are FIGS. 2A and 2B which are layer diagrams ofcorresponding portions of the structures shown in FIG. 1 as marked inFIG. 1 in the instance of FIG. 2A by a section line. These layerdiagrams give an indication of the structural layers leading to thestructures shown in FIG. 1 but are not true cross-section views in thatmany dimensions are exaggerated or reduced for purposes of clarity.

As indicated above, the signal isolator in connection with these figuresis provided on a substrate, 10, having a relatively smooth electricalinsulating layer, 11, of 2000 Å of silicon nitride (Si₃ N₄) providedthereover. Then, a 200 Å thick layer of tantalum (Ta), 11′, is providedon layer 11 as a starting material to be used in connection with thesubsequent provision of ferromagnetic material shields such as throughproviding a permalloy material (the remainder is shown in FIG. 2Afollowing etching to form those shields as described below).

A 2 μm shield layer of nickel iron alloy (NiFe), comprising 80% nickeland 20% iron, is sputter deposited on tantalum layer 11′. Then, as abasis for forming a mask to pattern this shield layer into magneticfield shields to provide magnetic shielding in connection with asubsequently provided coil and field sensors, a 500 Å thick layer ofsilicon nitride is provided on the shield layer and patterned using wellknown methods to form a mask covering the shield layer where shields areto be provided. The remaining exposed shield layer material is etchedaway to leave a pair of shields, 12, having a silicon nitride maskinglayer, 12′, thereupon.

Next, a 2 μm thick electrical insulating coil support layer, 13, isprovided using a positive photoresist polymer material, the materialbeing B-staged bisbenzocyclobutene (BCB) which is spun on over theshields present intermediate device structure to cover shields 12 stillsupporting the masking silicon nitride layer 12′, and to also cover theremaining exposed portions of tantalum layer 11′. This polymer materialbased layer is then heated to 250° C. in a hard curing step so that itthereafter exhibits sufficient mechanical stiffness to accommodatesubsequent steps in the fabrication process to further fabricate thedevice.

A mechanically stiff layer is next needed to be provided on deformablepolymer coil support layer 13 to provide a firmer base for bettersupporting the input conductor coil to be next provided, and forsupporting the bonding pads formed integrally with this coil (therebysubsequently allowing external interconnections to be made through wirebonding to this input conductor coil) while also adhering this coilstructure well to base polymer layer 13. Such a stiffening layer allowsfor successful wire bonding by limiting the movement in deformation ofthe bonding pad which otherwise would occur as layer 13 thereunder todeforms during wire bonding operations under the pressure applied insuch operations. Thus, a further silicon nitride layer, 13′, is providedby sputter deposition to a thickness of 5000 Å as such a stiffeninglayer on support layer 13.

Directly thereafter, a 2 μm layer of unalloyed aluminum is sputterdeposited onto silicon nitride stiffening layer 13′ from which to formthe input conductor coil and its bonding pads. Photoresist is thenprovided over this aluminum layer to be formed into an etch mask, andpatterned for this purpose using well known methods so as to leaveportions thereof at locations where the input conductor coil and thebonding pads integral to this coil are to result. Reactive ion etchingis used to remove the unmasked and unwanted portions of the aluminum soas to leave a coil, 14, and its integrally formed bonding pads, 14′, thelatter being shown in dash line form in not being at the surface throughwhich the section is taken in FIG. 2A. Thereafter, a protective layer,14″, of 5000 Å thick silicon nitride is deposited over coil 14, coilbonding pads 14′ and the exposed surfaces of silicon nitride stiffeninglayer 13′, this protective layer being provided to offer furtherstiffening and prevent water vapor transfer. The portion of this lastprovided silicon nitride layer that is over coil bonding pads 14′ is notindicated in FIG. 2A.

Upon completion of silicon nitride protective layer 14″, a 6.5 μmpositive photoresist polymer material layer is spun on over thisprotective layer. This spun on layer then is cured at a temperature 250°C. to provide a hardened polymer layer, 15. Layer 15 is the primary highvoltage isolation layer for the isolator and therefore must exhibit ahigh breakdown voltage, and with low water absorption in support of thisrequirement. Layer 15 should also improve the planarization of theresulting outer surface of this layer relative to the surfaces on whichit is formed, and it should adhere well to those surfaces. Again, thispolymer layer needs to exhibit sufficient mechanical stiffness to permitsubsequent operations in completing the fabrication of the device. Theglass transition temperature of layer 15 must be sufficiently high toexceed temperatures reached during thermosonic bonding. Here too, thephotoresist material BCB is chosen as a basis of providing layer 15.

Again, a mechanically stiff layer is then needed to be provided ondeformable polymer dielectric layer 15 to yield a firmer base forsupporting the structures to be provided in the remaining fabricationsteps in forming the final device. Thus, a silicon nitride layer, 15′,is provided by sputter deposition to a thickness of 200 Å onto primaryinsulating layer 15 to serve as a base for the current sensor structuresto be next provided.

The current sensor “sandwich” structure to be provided for the currentsensor just mentioned is started with a compatible base metal layer, 16,shown as the next to bottom layer in FIG. 2B which provides afragmentary view of such a sensor structure. This base layer is formedby sputter depositing a layer of primarily β-phase tantalum on layer15′. Layer 16 is typically deposited to a thickness of 40 Å as abuffering base layer for supporting a subsequent ferromagnetic materiallayer in the “sandwich” structure current sensor to subsequently beformed thereon, this layer to prevent material diffusion between that“sandwich” structure and silicon nitride layer 15′ below.

Upon buffer layer 16 is then deposited a 32.5 Å thick permalloy, orNiFe, layer, 17, to serve in the final current sensor “sandwich”structures as an added augmenting, interacting ferromagnetic material“free” layer. Layer 17 is deposited in the presence of a magnetic fieldhaving a magnitude of 20 Oe in an initial selected direction to orientthe induced easy axis of this layer in that direction.

A 45 Å thick tantalum spacer layer, 18, is next deposited on interacting“free” layer 17 to separate that layer from the next ferromagneticmaterial layer. That next layer, a 42.5 Å thick permalloy, or NiFe,layer, 19, is deposited on spacer layer 18, layer 19 to serve, after theetching to form the current sensor from these layers, as part of thesensing ferromagnetic material “free” layer in that sensor. Thedeposition of layer 19 is followed by depositing thereon a 10 Å thickcobalt iron, or CoFe, magnetoresistance enhancement layer, 20, on layer19 as the remainder of the sensing “free” layer, thus formed ascomposite layer, with both of these last two layers being deposited inthe presence of a magnetic field having a magnitude of 20 Oe in theinitial selected direction indicated above.

A copper layer, 21, that is 27.5 Å thick is then deposited on compositesensing “free” layer 19, 20 to form a nonmagnetic, electricallyconductive intermediate layer for this “giant magnetoresistive effect”device. Another cobalt iron layer, 22, is deposited to a thickness of42.5 Å as the “pinned” layer in being part of what will become amagnetization direction reference layer structure after the deviceformation etching, this layer being deposited in the presence of amagnetic field with a magnitude of 20 Oe which can either be oriented inthe initial selected direction indicated above or in a directionperpendicular thereto, here typically being the latter. Layer 22 has itsmagnetization direction “pinned” by depositing thereon anantiferromagnetic material to form a “pinning” layer, 23, as theremainder of the reference layer structure, also in the presence of amagnetic field with a magnitude of 20 Oe directed parallel to themagnetization direction chosen for layer 22. Layer 23 has for theantiferromagnetic material therein chrome platinum manganese, or CrPtMn,deposited to a thickness of 325 Å.

Thus, the magnetization direction reference layer is formed of “pinned”layer 22 and “pinning” layer 23 through exchange coupling therebetweento thereby establish a magnetization direction, even in the face ofexternally applied magnetic fields, in the finally formedmagnetoresistors providing the current sensors for the isolator. Atantalum interconnection buffer layer, 24, is then provided on “pinning”layer 23 to a thickness of 50 Å to protect the magnetoresistivestructure during subsequent fabrication steps, and to facilitate goodelectrical contact to the aluminum interconnection structures to beprovided thereto.

This spin-valve current sensor is provided with second “free”ferromagnetic material layer 17 as contrasted with the usual single freelayer in such a device. Composite “free” layer 19, 20 is the sensinglayer which contributes to the sensor giant magnetoresistive effectresponse while second “free” layer 17 is an interacting layer whichinfluences the performance of sensing layer 19, 20 but does notcontribute to the sensor giant magnetoresistive effect response. Thisarrangement not only can significantly reduce the hysteresis of thecomposite free layer but also provides a means to adjust and optimizethe bias point of this linear spin-valve sensor through suitablyselecting the thickness of interaction layer 17.

Following provision of these layers to form the described stack, anannealing step is undertaken. The substrate and the stack are heated inthe presence of a magnetic field with a magnitude of 3000 Oe in theinitial selected direction with this field being maintained during onehour heating at 250° C. in forming gas, and during the subsequentcooling. This is done for the purposes of strengthening the pinning oflayer 22 by layer 23, and for reducing the dispersion of the angularorientations of the easy axes from the initial selected direction, orthe direction perpendicular thereto, over the extents thereof.

The magnetoresistor structures for the isolator current sensors areformed from this stack of deposited layers through a patterning etchingprocess. An etching mask of silicon nitride is provided through usingpatterned photoresist as an initial etching mask for patterning thesilicon nitride in a reactive ion etcher (RIE) and then using theresulting silicon nitride “hard mask” as an etching mask in an ion mill.The ion mill will remove all materials in the deposited electricallyconductive layers not covered by the “hard mask” material, and soexposed to the etching, beginning first with the material in layer 24,not covered by the mask, and then in each layer below those portions oflayer 24 are also etched away down to silicon nitride layer 15′ to leavethe crenelated magnetoresistor structures, i.e. the “sandwich” currentsensor structures, 25, shown in FIGS. 1 and 2A. Much of the siliconnitride forming the hard mask is also removed in the ion milling step.

A passivating silicon nitride layer, 26, is sputter deposited overmagnetoresistor structures 25 to a thickness of 5000 Å. Photolithographyis used to form etching mask for using reactive ion etching to opencontact holes in passivating layer 26 to magnetoresistor structures 25.Aluminum interconnection metal is sputter deposited over the remainingportions of passivation layer 26 and into the open contact holes overmagnetoresistors 25 to a thickness of 2 μm. This aluminum layer is thenpatterned using a photoresist etching mask and reactive ion etchingagain to provide aluminum interconnections, 27. A final passivatinglayer, 28, of silicon nitride is provided by sputter deposition to athickness of 1.5 μm which is omitted from being shown in FIG. 1.Aluminum interconnections 27 are shown in FIG. 1 ending, at those endsthereof not connected to crenelated magnetoresistor structures, orcurrent sensor, 25, so as to each terminate in a corresponding one offour bonding pads in a left to right sequence in a lower part of theview therein across from coil 14 and those magnetoresistors. The outertwo of these bonding pads are for supplying electrical current throughthe bridge circuit in which all four of magnetoresistors 25 areconnected, each in a different “leg” thereof, and the inner two of thesebonding pads are the output signal provision locations for the bridgecircuit, and hence for the signal isolator.

A masking layer 1000 Å thick of aluminum nitride (AlN) is then sputterdeposited over layer 28 and patterned using well known photolithographymethods. The patterning provides an opening in the aluminum nitride maskover the bonding pads 14′ through which an etching step is undertaken byreactive ion etching to remove the exposed corresponding portions ofsilicon nitride layers 28, 26 and 15′, and then the correspondingportion of primary insulating layer 15, and finally protective layer 14″to complete via openings, 29, to bonding pad 14′. The aluminum nitridemask portions remaining after the patterning of the precursor layer arealso removed in a subsequent wet chemical etching process.

Again, an annealing of the resulting magnetoresistors is performed,first, in the presence of a magnetic field with a magnitude of 3000 Oein the initial selected direction now along the lengths of themagnetoresistors with this field maintained during a one hour heating at240° C. in forming gas and during the subsequent cooling to reduce thedispersion of the angular orientations of the easy axes from the lengthsof the magnetic material layers over the extents thereof. A furtherannealing step follows in the presence of a magnetic field with amagnitude of 3000 Oe perpendicular to the initial selected direction,and so along the widths of the resulting magnetoresistors, with thisfield maintained during a two hour heating at 240° C. in forming gas,and then at 265° C. for one hour, to reorient the pinned direction oflayer 26 to be along with width of the magnetoresistors.

The annealing is completed in a further step in the presence of amagnetic field with a magnitude of 3000 Oe parallel to the initialselected direction, and so along the lengths of the resultingmagnetoresistors, with this field maintained during a two hour heatingat 160° C. in forming gas and during the subsequent cooling to reducethe dispersion of the angular orientations of the easy axes in freelayer 24 from the initial selected direction over the extent thereof butat a reduced temperature to avoid affecting the direction of pinning setin layers 26 and 27. These last two annealing steps result in a pinningdirection orientation at some relative angle to the widths of themagnetoresistors to thereby provide a component of the interlayercoupling along the lengths thereof to provide some bias to aid inminimizing the device hysteresis.

Completion of these fabrication steps on the wafer leaves the “dicing”of the wafer to yield the individual signal isolators which are thenmounted on an isolator lead frame. Typically, the isolator coupledoutput signal is provided to a receiver integrated circuit chip providedon a separate receiver lead frame with wire bonds extending from thefour interconnections 27 bonding pads, i.e. the bridge circuit formed byinterconnected magnetoresistors 25, to the receiver chip circuitry. Theouter two of these pads through which operating current is supplied tothe bridge circuit would optionally not have to be wire bonded to thereceiver chip but could, instead, be bonded to current supply pointsprovided in the receiver lead frame arrangement to avoid having suchcurrents in that chip.

This assembly of the two lead frames supporting the wire bondinterconnected isolator and receiver chips is typically encapsulated ina plastic housing to complete the signal isolator system. In a furtheralternative, rather than having the input being a wire bond from a leadframe pin to which pin an external signal source is coupled, a furthertransmitter monolithic integrated circuit chip can be providedcontaining circuitry that provides suitable signal conditioning to inputsignals received from an outside signal source to thereby supplysuitable signals for operating coil 14. This transmitter chip has wirebond interconnections with coil 14 on the isolator chip, and can beprovided on the same lead frame on which the isolator chip is providedwhile still leaving them both isolated from the receiver chip. Ofcourse, such a transmitter chip can be provided on a third lead framethat is in a common assembly with the other two all housed by a commonmass of encapsulating plastic.

Alternative to the structure shown in FIGS. 1 and 2, coil 14 can be moreconveniently and more uniformly provided as part of the lastmetallization interconnection layer provided in a monolithic integratedcircuit chip serving as a substrate for the remainder of the signalisolator device as well as providing the operating circuitry therefor.Further, there is then no need for large bonding pads 14′ for coil 14required to be provided beneath polymer insulating layer 15 since thecoil is interconnected to the operating circuitry in the chip therebyallowing a reduction in chip surface area. Such an arrangement is shownin FIG. 3 where portions thereof that are closely similar to portions inFIG. 1 retain the same numerical designations in FIG. 3 they had in FIG.1.

Bonding pads 14′ of FIGS. 1 and 2 are shown replaced in FIG. 3 byinterconnections, 14′″, extending through via openings in the integratedcircuit insulation layer supporting coil 14 and other structures thereinbelow that insulation layer to connect coil 14 to the circuitry in themonolithic integrated circuit chip of the substrate. Thus, coil 14 isinterconnected with the integrated circuitry entirely under polymerinsulating layer 15 thereby eliminating the need for vias 29.

On the other hand, electrical power and an interconnection to anexternal input signal source are required by the integrated circuitrywithin the monolithic integrated circuit chip both for the operation ofthat circuit, and for the supply of information signals to be coupledfrom the input of the signal isolator to the output thereof across theisolation barrier. Thus, further vias, 29′, are shown in FIG. 3extending from the system outer surface to bonding pads in theintegrated circuit chip to allow for thermosonic wire bonding from chiphousing terminals to those bonding pads in the monolithic integratedcircuit to provide interconnections for supplying positive and negativeoperating voltage to the monolithic integrated circuit chip and furthersupplying input signals to be coupled to the signal isolator output.

Such an arrangement, however, makes providing shields 12 of FIGS. 1 and2, positioned there between coil 14 and substrate 10, infeasible due tothe required thickness thereof. One arrangement for an alternativemagnetic shield is to provide a shielding layer of ferromagnetic metalmaterial such as permalloy that is plated onto the side of thesemiconductor chip containing the monolithic integrated circuit foroperating the isolator that is opposite that on which the coil isprovided, although this can be a difficult fabrication to achieve asuitably aligned shield. Other possibilities are indicated in the layerdiagrams of FIGS. 4A and 4B, taken in the alternative from FIG. 3 asindicated in that figure, showing magnetic shielding being provided byeither the lead frame on which the semiconductor integrated circuit chipincluding the signal isolator portions thereof is mounted for use (whichwould require that frame to be made of a ferromagnetic material), or bya ferromagnetic material plate attached to a typical commerciallyavailable lead frame on which the chip is mounted for subsequent use.

Once a monolithic integrated circuit wafer including the individual chipcircuits is available with each including a coil 14 therein, thefabrication of the remainder of the signal isolator system is completedessentially as above but starting at the point in the fabricationprocess at which insulating polymer layer 15 in FIGS. 1 and 2 isprovided. Those portions of FIGS. 4A and 4B closely similar to portionsshown in FIG. 2A retain the same numerical designations in FIGS. 4A and4B as they had in FIG. 2A.

In FIG. 4A, the numerical designation 10 refers to the entire substrateincluding the semiconductor chip containing the monolithic integratedcircuit and the last electrical insulating layer below the metallizationlayer from which coil 14 is formed along with coil integrated circuitinterconnections, 14′″. The same situation is shown in FIG. 4B. In eachof these figures, substrate 10 is supported on a lead frame which inFIG. 4A is a lead frame, 10′, made of permalloy, and which in FIG. 4B isa typical commercially available lead frame, 10″, that is, an ordinarycopper alloy lead frame commercially available. In this latter instancein FIG. 4B, however, a further layer is shown comprising a permalloymaterial shield, 10′″, which is affixed beneath lead frame 10″.

The occurrence or application of a magnetic field external to the signalisolator system as supported on a substrate will cause the magnetizationof the magnetically permeable material in any of these shields to rotatetoward aligning with this external field, and this realignedmagnetization will result in a demagnetization field being establishedby the shield material in this situation. The tendency of thisdemagnetization field to cancel the external field in adjacent regionsalong perpendiculars to the external field provides the shielding effectwith respect to that external field in those regions. FIG. 5 shows anapproximation to a plate-like shield structure which allows estimatingthe magnitude of the demagnetization field H_(d) in the regions adjacentto the wide sides of the plate in the situation of an external uniformmagnetic field of magnitude Ha being applied. Such an external fieldwill lead to a magnetic surface charge density σ({right arrow over(r)}_(n)) occurring on areas A₁ and A₂ (n=1,2) in the absence of anybulk charge in the shield to give rise to a correspondingdemagnetization field which can be determined from${{H_{d}(r)} = {{\int_{A_{1}}^{\quad}{\frac{\sigma\left( {\overset{\rightarrow}{r}}_{1} \right)}{{{\overset{\rightarrow}{r} - {\overset{\rightarrow}{r}}_{1}}}^{2}}{\mathbb{d}A_{1}}}} + {\int_{A_{2}}^{\quad}{\frac{\sigma\left( {\overset{\rightarrow}{r}}_{2} \right)}{{{\overset{\rightarrow}{r} - {\overset{\rightarrow}{r}}_{2}}}^{2}}{{\mathbb{d}A_{2}}.}}}}}\quad$The magnetic surface charge density for a uniform magnetic field H_(a)will be constant of a value σ on each of surfaces A₁ and A₂, though ofopposite polarity, and so the preceding equation can be written inCartesian coordinates as${H_{d}\left( {x,y,z} \right)} = {{\int{\int{\frac{\sigma\left\lbrack {{\left( {x - x_{1}} \right){\overset{\rightarrow}{e}}_{x}} + {\left( {y - y_{1}} \right){\overset{\rightarrow}{e}}_{y}} + {\left( {z - z_{1}} \right){\overset{\rightarrow}{e}}_{z}}} \right\rbrack}{{{\left( {x - x_{1}} \right)^{2} + \left( {y - y_{1}} \right)^{2} + \left( {z - z_{1}} \right)^{2}}}^{3/2}}{\mathbb{d}y_{1}}{\mathbb{d}z_{1}}}}} - {\int{\int{\frac{\sigma\left\lbrack {{\left( {x - x_{2}} \right){\overset{\rightarrow}{e}}_{x}} + {\left( {y - y_{2}} \right)\overset{\rightarrow}{e}} + {\left( {z - z_{2}} \right){\overset{\rightarrow}{e}}_{z}}} \right\rbrack}{{{\left( {x - x_{2}} \right)^{2} + \left( {y - y_{2}} \right)^{2} + \left( {z - z_{2}} \right)^{2}}}^{3/2}}{\mathbb{d}y_{2}}{\mathbb{d}z_{2}}}}}}$where {right arrow over (e)}_(x), {right arrow over (e)}_(y) and {rightarrow over (e)}_(z) represent unit vectors along the coordinate systemaxes and x₁, x₂, y₁, y₂, z₁ and z₂ represent the coordinate extentlimits of the plate-like shield structure or w/2, −w/2, 1/2, −1/2, t/2and −t/2, respectively. If the shield is taken as extending so far inits length along the y axis from the region to be shielded as to bereasonably considered to be of infinite length as is usuallyapproximately true, the foregoing equation can be integrated over y soas to remove the y coordinate dependency giving${{H_{d}\left( {x,z} \right)} = {{2\sigma{\int_{- \frac{1}{2}}^{+ \frac{1}{2}}{\frac{{\left( {x - x_{1}} \right){\overset{\rightarrow}{e}}_{x}} + {\left( {z - z_{1}} \right){\overset{\rightarrow}{e}}_{z}}}{\left( {x - x_{1}} \right)^{2} + \left( {z - z_{1}} \right)^{2}}{\mathbb{d}z_{1}}}}} + {2\sigma{\int_{- \frac{1}{2}}^{+ \frac{1}{2}}{\frac{{\left( {x - x_{2}} \right){\overset{\rightarrow}{e}}_{x}} + {\left( {z - z_{2}} \right){\overset{\rightarrow}{e}}_{z}}}{\left( {x - x_{2}} \right)^{2} + \left( {z - z_{2}} \right)^{2}}{\mathbb{d}z_{2}}}}}}}\quad$where the extent of the thickness along the z axis is indicated in thelimits of the integrals. Integrating the terms in which the numeratorhas z or z, within it leads to results in the two integrals that cancelone another leaving${{H_{d}\left( {x,z} \right)} = {{2\sigma{\int_{- \frac{1}{2}}^{+ \frac{1}{2}}{\frac{\left( {x - x_{1}} \right){\overset{\rightarrow}{e}}_{x}}{\left( {x - x_{1}} \right)^{2} + \left( {z - z_{1}} \right)^{2}}{\mathbb{d}z_{1}}}}} + {2\sigma{\int_{- \frac{1}{2}}^{+ \frac{1}{2}}{\frac{\left( {x - x_{2}} \right){\overset{\rightarrow}{e}}_{x}}{\left( {x - x_{2}} \right)^{2} + \left( {z - z_{2}} \right)^{2}}{{\mathbb{d}z_{2}}.}}}}}}\quad$

Since the x terms are not involved in the above integration, the xcoordinate dimension limits of x, =w/2 and x₂=−w/2 can be inserted togive${{H_{d}\left( {x,z} \right)} = {{2\sigma{\int_{- \frac{1}{2}}^{+ \frac{1}{2}}{\frac{\left( {x - \frac{w}{2}} \right)}{\left( {z - z_{1}} \right)^{2} + \left( {x - \frac{w}{2}} \right)^{2}}{\mathbb{d}z_{1}}}}} + {2\sigma{\int_{- \frac{1}{2}}^{+ \frac{1}{2}}{\frac{\left( {x + \frac{w}{2}} \right)}{\left( {z - z_{2}} \right)^{2} + \left( {x - \frac{w}{2}} \right)^{2}}{{\mathbb{d}z_{2}}.}}}}}}\quad$This expression can then be integrated to yield${H_{d}\left( {x,z} \right)} = {{2\left( {x - \frac{w}{2}} \right){\sigma\left\lbrack {\frac{1}{x - \frac{w}{2}}\tan^{- 1}\frac{\left( {z_{1} - z} \right)}{x - \frac{w}{2}}} \right\rbrack}_{- \frac{t}{2}}^{+ \frac{t}{2}}} - {2\left( {x + \frac{w}{2}} \right){\sigma\left\lbrack {\frac{1}{x + \frac{w}{2}}\tan^{- 1}\frac{\left( {z_{2} - z} \right)}{x + \frac{w}{2}}} \right\rbrack}_{- \frac{t}{2}}^{+ \frac{t}{2}}}}$or, after evaluating,${H_{d}\left( {x,z} \right)} = {{2{\sigma\left\lbrack {{\tan^{- 1}\frac{z + \frac{t}{2}}{x - \frac{w}{2}}} - {\tan^{- 1}\frac{z - \frac{t}{2}}{x - \frac{w}{2}}}} \right\rbrack}} - {2{{\sigma\left\lbrack {{\tan^{- 1}\frac{z + \frac{t}{2}}{x + \frac{w}{2}}} - {\tan^{- 1}\frac{z - \frac{t}{2}}{x + \frac{w}{2}}}} \right\rbrack}.}}}$This equation can be used to show that two shields of 2.0 μm thickpermalloy which saturate in a field of 160 Oe provide adequate shieldingin the arrangement provided for the signal isolator of FIG. 2A. Thereis, of course, more freedom to add to the size of the shields in FIGS.4A and 4B as the shields there are formed without the limitationsencountered in providing shielding using integrated circuit fabricationprocess as was done in providing the structure of FIGS. 1 and 2A.

FIGS. 1 through 4 show, as indicated above, signal isolators with themain device structural components, beginning with a shield, either onthe chip or the lead frame, followed by a planar coil, an insulatinglayer and then magnetoresistors as current sensors, these componentsstacked in that order on the supporting substrate. As stated above, thisis a reverse of the stacking order for these main device structuralcomponents that had previously been used. However, rather than forming asignal isolator from these main device structural components in just oneof these orders or the other to couple signals past an isolation barrierto the magnetoresistors output circuit, plural signal isolators can bejointly formed in a single isolator chip structure that will then allowbidirectional transmissions between two communicating entities. Thisrequires that such an isolator chip have at least two signal isolatorstherein each formed using a different one of these device structuralcomponent orders so that a transmitter and a receiver for each entitycan be provided in common on a chip that is on the same side of theisolation barrier but across that barrier from the other entity havingits transmitter and receiver provided in a different chip.

The use of the two different stacking structures in the two signalisolators aids in keeping the main device structural components of eachseparated by layers from one another to maintain good electricalisolation therebetween. Further, the use of two different stackingstructures positions the input of one isolator near the output of theother which together will be connected to the same one of twocommunicating entities in typical operation and so are likely to have arelatively small voltage difference therebetween to again to aid inmaintaining good electrical isolation between isolator components.

Such an arrangement allows such an isolator chip along with atransmitter-receiver chip to each be housed on a corresponding one oftwo lead frame portions provided in some housing, separated and soelectrically isolated from one another, to thereby provide bidirectionalcoupling of input signals to isolated outputs between the twocommunicating entities while keeping them electrically isolated from oneanother. That is, the input and output of one communicating entity areconnected to the output and input of one transmitter-receiver chip wirebonded to the isolator chip, and the input and output of the other ofthese two communicating entities is connected to the output and input ofthe transmitter and receiver provided on the isolator chip or,alternatively, provided on another transmitter-receiver chip again wirebonded to the isolator chip.

Such an isolator chip is shown in the fragmentary plan view thereof inFIG. 6 formed on a ceramic or silicon substrate as is done with thesignal isolator of FIGS. 1, 2, 3 and 4 again with the outer protectiveor passivating layer not being shown. The signal isolator shown on theright in FIG. 6 is generally similar to the one shown in FIG. 1, or isessentially so, as can be seen in comparing the corresponding layerdiagram of FIG. 7A with that of FIG. 2A. The signal isolator on the leftin FIG. 6 is formed using the main device structural component stackingsequence used heretofore having the magnetoresistors, or currentsensors, nearest the substrate followed by an insulating barrier layerand then the coil and shields as shown in the layer diagram of FIG. 7B.

The layers that are the same in each of the layer diagrams of FIG. 7Aand FIG. 7B have the same numerical designation in each figure tothereby indicate they are commonly formed in the device fabricationprocess. The layers in FIG. 7A corresponding to similar layers in FIG.2A have the same numerical designations there that they did in FIG. 2A,and are formed in essentially the same manner as in the device of FIG.2A although some differences in layer thicknesses and other aspects arepresent. The signal isolator main device structural components includingshield 12, coil 14, coil bonding pads 14′ and magnetoresistors 25, andalso metallization interconnections 27, retain the same designations inFIG. 7A they had in FIG. 2A. The counterparts to these components,provided in the stacking order shown in FIG. 7B that is reversed to thatshown in FIG. 7A, have an “r” added thereafter in FIG. 7B to indicatethey are for the reverse signal coupling direction in the isolator chip(and that the main components have the reverse stacking order on thesubstrate). This leads to FIG. 7B showing reversed stacking orderposition shields, 12 r, a reverse coil, 14 r, with bonding pads 14′r,and a set of reverse magnetoresistors, 25 r, along with correspondingmetallization interconnections, 27 r.

Some additional layers are provided in the device of FIGS. 7A and 7Bover those shown for the device in FIG. 2A because of the need toaccommodate the provision of an added coil, i.e. to protect coil 14 r,the provision of added shields, i.e. to provide a plating start layerfor shields 12 r, and the provision of added magnetoresistors andcorresponding metallization interconnections, i.e. protectingmagnetoresistors 25 r and interconnections 27 r. Thus, a further siliconnitride layer, 13″, provided by sputter deposition to a thickness of2500 Å is added for forming magnetoresistors 25 r and interconnections27 r in FIG. 7B, and so this layer appears also in FIG. 7A even thoughnot present in FIG. 2A because of the fabrication process being commonto each device portion shown in FIGS. 7A and 7B.

Further, a 2 μm polymer electrical insulating layer, 30, is providedover layer 28 in FIG. 7B with the polymer material for this layer againbeing BCB. A stiffening layer of silicon nitride, 31, is then depositedon layer 30 with a thickness of 5000 Å. Finally, a 500 Å permalloy layeris provided as a plating start layer for having shields 12 r platedthereon with just the remainders of that layer, 32, shown in FIG. 7B asremnants resulting after the etching of the shields following platingthe layer therefor on the plating start layer.

The device of FIGS. 6, 7A and 7B is formed using three layers ofelectrical insulating polymer material BCB to thereby control uniformityof the separation between coils and their corresponding magnetoresistorswell and uses just two added layers of metallization. As the kinds offabrication process steps used here are the same as those used forforming the device of FIGS. 1 and 2, the fabrication process with bepresented only in summary here. The fabrication process begins withforming shields 12, for the one signal isolator that is essentially thesame as the device forming the FIG. 2A signal isolator, by sputterdepositing permalloy therefor tantalum layer 11′, and the wafer is thenreplanarized through providing the first layer of BCB that is 2.0 μmthick, layer 13. Silicon nitride is next deposited to a 500 Å thicknessas base layer 13′ for forming magnetoresistors 25 r of the otherisolator, this layer provision next followed by forming thosemagnetoresistors and part of the bridge circuit in which they are to beprovided. After passivating magnetoresistors 25 r with a silicon nitridelayer 13″ and opening windows therein, aluminum metal forinterconnections 27 r and metal for coil 14 is deposited, patterned andprotected with further silicon nitride layer 14″ that is 2,000 Å thick.

The primary isolation layer of BCB for both isolators is then spun onand cured as second BCB layer 15 to a 8.0 μm thickness followed bysputtering stiffening silicon nitride layer 15′ to a thickness of 500 Å.Magnetoresistors 25, including part of the bridge circuit therefor, areprovided as before and then passivated by sputtering thereon siliconnitride layer 26 to a thickness of 2500 Å. After opening vias to thesemagnetoresistors, a second layer of aluminum is deposited and patternedto provide coil 14 r and interconnections 27 including completing thebridge circuit for these magnetoresistors. Protective layer 28 ofsilicon nitride is then sputtered on to a thickness of 2500 Å.

Final passivation with a third BCB layer 2.0 μm thick is providedthrough being spun on and cured by heating, this being layer 30, whichis then covered by silicon nitride stiffening layer 31 to a depth of5000 Å. A permalloy plating start layer is then deposited by sputteringto a thickness of 500 Å with permalloy shields 12 r then being platedand patterned along with plating start layer 32. An aluminum nitridehard mask process is used to pattern the vias 29, 29 r and those to thebridge circuits over the bonding pads made by metallizationinterconnections 27.

In the resulting device, coils 14 and 14 r are separated by 8 μm of BCBfor good electrical isolation but the electrical isolation between thetwo isolator main device structural component stacks must again bemaintained through sufficient lateral spatial separation between thosemagnetoresistors and metal interconnections of one isolator and the coilof the other which are together provided separated in each instance by asilicon nitride layer 13″ in the lower location instance in FIG. 7B andby silicon nitride layer 26 in the upper location instance in FIG. 7A.Separation can be reduced by thickening these silicon nitride layers orby substituting other, better, or additional, insulating material. Useof a suitable polymer material, such as BCB, allows omitting siliconnitride protective layers 14″ and 28.

An alternative isolator chip, also having two signal isolators each withthe main device signal components thereof stacked in opposite orderagain formed on a ceramic or silicon substrate, is shown in thefragmentary plan view of that chip provided in FIG. 8 with the outerprotective or passivating layer once more omitted in that view forclarity. Here too, the signal isolator shown on the right in FIG. 8 isin essence similar to the signal isolator shown in FIG. 1, a situationthat is reflected in the similarity between the layer diagram of FIG. 9Acorresponding to FIG. 8 and that of FIG. 2A. The signal isolator on theleft in FIG. 8 is shown in the corresponding layer diagram of FIG. 9B tohave the main device structural components thereof in the stacking orderused in signal isolators used heretofore, that is, with themagnetoresistors, or current sensors, being nearest the substrate andhaving an insulating barrier layer stacked thereon which in turn has acoil and shields stacked in that order on that barrier.

Again, the layers that are the same in each of the layer diagrams ofFIGS. 9A and 9B have the same numerical designation in each of thosefigures, in view of them having been commonly formed in the devicefabrication process, to thereby allow their relative positions in eachportion of the isolator chip shown in those figures to be easily seen.The layers in FIG. 9A correspond to similar layers in FIG. 2A and sohave been given the same numerical designations in this figure that theyhad in FIG. 2A. They are again formed in essentially the same manner asthey are formed in the device of FIG. 2A although again with somedifferences in layer thicknesses and other aspects thereof beingpresent.

The signal isolator main device structural components in FIG. 9A, shield12, coil 14, coil bonding pads 14′ and magnetoresistors 25 along withmetallization interconnections 27, retain the same designations in thatfigure that were used for them in FIG. 2A (and also in FIG. 7A). Themain device structural components for the signal isolator shown in FIG.9B, being in the reverse stacking order on the substrate from thoseshown in FIG. 9A, again have an “r” added thereafter in FIG. 9B toindicate a stacking order and signal transmission direction reversal inthis isolator as was done in FIG. 7B. Hence, FIG. 9B shows shields 12 r,coil 14 r and coil bonding pads 14′r, magnetoresistors 25 r andcorresponding metallization interconnections 27 r.

This configuration also requires additional layers being provided in thedevice of FIGS. 9A and 9B beyond those shown for the device in FIG. 2Afor again the same reasons of needing to accommodate the provision ofadded shields 12 r and added magnetoresistors 25 r along withcorresponding metallization interconnections 27 r though not for addedcoil 14 r. Two further silicon nitride layers, 11′″ and 11″″, areprovided for forming magnetoresistors 25 r along with interconnections27 r in FIG. 9B. These two layers appear also in FIG. 9A even thoughthey are not present in FIG. 2A because of the fabrication process beingcommon in each device portion shown in FIGS. 9A and 9B. These layers areeach provided by sputter deposition to a thickness of 2000 Å. Again, a500 Å permalloy layer is provided as a plating start layer as a basisfor having shields 12 r plated thereon with just the remainders of thatlayer, designated 32 as before, shown in FIG. 9B as remnants resultingfrom the etching process of the shields following plating the layertherefor on the plating start layer.

A 2000 Å thick silicon nitride layer 14″ is provided over coil 14 justas in FIG. 2A, and also over coil 14 r which are formed on the samesilicon nitride layer 13′, but here silicon nitride layer 13′ is 2000 Åthick to provide a more stiffening support for these coils. Coils 14 and14 r, being provided on the common base of silicon nitride layer 13′,must be kept relatively widely separated to be able to maintain goodelectrical isolation therebetween in view of the possibility they mayeach be operated at substantially different voltage levels. Addinganother insulating layer over one coil as a base for forming the otherto provide more insulating material between them can reduce such aseparation spacing requirement.

A summary of the fabrication process for the two polymer material layerdevice of FIGS. 8, 9A and 9B begins with forming magnetoresistors 25 rand part of the bridge circuit in which they are connected on 200 Åthick silicon layer 11″ followed by sputter depositing a 3,000 Å thicksilicon nitride passivating layer 11′″ thereon. An aluminuminterconnection layer 18,000 Å thick is next deposited and patterned toform interconnections 27 r, which are then protected by a deposited3,000 Å thick silicon nitride layer 11 “ ”. Next, a 200 Å thick tantalumlayer is deposited as the basis for supporting shields 12, and 2.0 μm ofpermalloy is sputtered thereon and patterned to form shields 12 andremnants 11′ of the tantalum layer.

Polymer electrical insulating layer 13 is then spun on and cured byheating using again BCB to provide an isolation barrier 8.0 μm thickfollowed by sputter depositing silicon nitride stiffening layer 13′ thatis 2,000 Å thick to support coils 14 and 14 r. Then 2.0 μm of aluminumis sputter deposited on this nitride layer for coils 14 and 14 r andpatterned. After protecting these coils with layer 14″ of siliconnitride 2,000 Å thick (which again can be omitted for subsequent use ofa suitable barrier layer polymer such as BCB), second polymer materialisolation barrier layer 14 of BCB is spun on and cured to a thickness of8.0 μm.

A 200 Å thick silicon nitride layer 15′ is sputter deposited as a basisfor forming magnetoresistors 25 and part of the bridge circuit in whichthey are connected. After passivating by sputter depositing 2,000 Åthick silicon nitride layer 26 and opening interconnection vias therein,an aluminum layer 18,000 Å thick is deposited and patterned to createinterconnections 27 to complete the bridge circuit including providingsignal runs from the bridge circuit junctions to bonding pads. Afterfinal passivation layer 28 is provided by sputter depositing 2,000 Å ofsilicon nitride, a plating start layer 32 of 500 Å of permalloy issputter deposited upon which shields 12 r are then plated. An aluminumnitride hard mask is then used to open the vias to all of the bondingpads. Thus, three separate isolation zones are established by the use oftwo polymer material layer isolation barriers.

As seen in FIGS. 8 and 9B, vias 29 r are provided to allow thermosonicwire bonds to be made to coil bonding pads 14′r of coil 14. The need tomake such wire bonds through such relatively deep vias can be eliminatedfor the signal isolator of FIG. 9B by providing a portion of theinterconnections of these pads to the outer surface region by openingvias to coil bonding pads 14′r before forming shields 12 r and thenproviding these shields so as to also fill the vias to coil bonding pads14′r with conductive metal joined to the shields thereby making theshields also the coil bonding pads.

Thus, as seen in the fragmentary plan view of FIG. 10, a chip portion isshown corresponding to the portion of the chip provided in FIG. 8corresponding to FIG. 9B before the modification thereof now seen inFIG. 10. Coil bonding pads 14′r of FIG. 8 are gone, they being replacedin FIG. 10 by much smaller interconnection pads, 14“ ”. In the layerdiagram of FIG. 11 corresponding to FIG. 10, an interconnection, 12′r,extends from each of shields 12 r to a corresponding one ofinterconnection pads 14″″ so that these shields can be bonding pads forhaving thermosonic bonds provided thereon from which signal currents canbe established therein and in interconnections 12′r, interconnectionpads 14″″, and coil 14. Interconnections 12′r are provided by formingvias through plating start layer 32, silicon nitride layers 28 and 26,polymeric insulating material layer 15 and silicon nitride layer 14″,and then beginning and completing the plating of shields 12 r whichprovides interconnections 12′r as well as shields 12 r.

Although the present invention has been described with reference topreferred embodiments, workers skilled in the art will recognize thatchanges may be made in form and detail without departing from the spiritand scope of the invention.

1. A current determiner for providing at an output thereofrepresentations of input currents provided therein from sources of suchcurrents, said current determiner comprising: a substrate; an firstinput conductor supported on said substrate suited for conducting saidinput currents therethrough; a first shield/concentrator layer ofmaterial exhibiting a substantial magnetic permeability and positionedat that side of said first input conductor facing said substrate toserve as a magnetic field concentrator; and a first current sensorsupported on said substrate on a side of said first input conductoropposite that said side thereof facing said substrate so as to beadjacent to, yet spaced apart from, said first input conductor at anopposite side thereof to thereby be electrically isolated from anydirect circuit interconnection therewith on said substrate butpositioned in those magnetic fields arising from said input currents,said first current sensor being formed of a plurality ofmagnetoresistive, anisotropic, ferromagnetic thin-film layers at leasttwo of which are separated from one another by a nonmagnetic layerpositioned therebetween.
 2. The apparatus of claim 1 wherein one of saidtwo ferromagnetic thin-film layers has a magnetization that issubstantially maintained in a selected direction despite said magneticfields arising from said input currents causing reversals of directionof magnetization of that remaining one of said two ferromagneticthin-film layers.
 3. The apparatus of claim 1 wherein said twoferromagnetic thin-film layers have magnetizations at least one of whichchanges in direction of magnetization due to said input currents withrespect to that direction thereof occurring due to a biasing electricalcurrent therethrough absent any said input currents occurring in saidfirst input conductor.
 4. The apparatus of claim 1 wherein one of saidtwo ferromagnetic thin-film layers has a magnetization that issubstantially maintained in a selected direction despite said magneticfields arising from said input currents causing changes in direction ofmagnetization of that remaining one of said two ferromagnetic thin-filmlayers, and further including a third ferromagnetic thin-film layerspaced apart from that remaining one of said two ferromagnetic thin-filmlayers on a side thereof opposite that side across from which ispositioned said ferromagnetic thin-film layer having a magnetizationthat is substantially maintained in a selected direction.
 5. Theapparatus of claim 1 wherein said first shield/concentrator layer issupported on said substrate between said first input conductor and saidsubstrate.
 6. The apparatus of claim 1 wherein a housing therefor has asupport structure supporting said current determiner that is formed of amagnetically permeable material to serve as said firstshield/concentrator layer.
 7. The apparatus of claim 1 wherein a housingtherefor has a support structure supporting said current determiner thathas a shield structure attached thereto that is formed of a magneticallypermeable material to serve as said first shield/concentrator layer. 8.The apparatus of claim 1 further comprising a receiver integratedcircuit chip having output signal processing circuitry therein that iselectrically interconnected to said first current sensor but otherwiseelectrically isolated from said current determiner including saidsubstrate thereof.
 9. The apparatus of claim 1 further comprising aninput converter integrated circuit chip having input signal processingcircuitry therein that is electrically interconnected to said firstinput conductor but otherwise electrically isolated from said currentdeterminer including said substrate thereof.
 10. The apparatus of claim1 further comprising a second current sensor supported on said substratewith said second current sensor being formed of a plurality ofmagnetoresistive, anisotropic, ferromagnetic thin-film layers at leasttwo of which are separated from one another by a nonmagnetic layerpositioned therebetween, a second input conductor supported on saidsubstrate suited for conducting input currents of said sourcestherethrough and positioned at that side of said second current sensoropposite to that side thereof facing said substrate so as to be adjacentto, yet spaced apart from, the second current sensor to thereby beelectrically isolated from any direct circuit interconnection therewithon said substrate but to have said second current sensor positioned inthose magnetic fields arising from said input currents in said secondinput conductor, and a second shield/concentrator layer of materialexhibiting a substantial magnetic permeability to serve as a magneticfield concentrator and positioned at that side of said second inputconductor opposite to that side thereof facing said substrate.
 11. Theapparatus of claim 1 wherein said substrate further comprises amonolithic integrated circuit structure containing electronic circuitcomponents of which at least one is electrically connected to said firstinput conductor.
 12. The apparatus of claim 1 further comprising asecond current sensor supported on said substrate adjacent to, yetspaced apart from, said first input conductor to thereby be electricallyisolated from any direct circuit interconnection therewith on saidsubstrate but positioned in those magnetic fields arising from currentsoccurring in said first input conductor, said second current sensorbeing formed of a plurality of magnetoresistive, anisotropic,ferromagnetic thin-film layers at least two of which are separated fromone another by a nonmagnetic layer positioned therebetween.
 13. Theapparatus of claim 10 wherein said first and second input conductors areprovided at substantially a common surface within said currentdeterminer.
 14. The apparatus of claim 10 wherein said first and secondinput conductors are provided on different surfaces separated from oneanother within said current determiner.
 15. The apparatus of claim 10wherein said substrate further comprises a monolithic integrated circuitstructure containing electronic circuit components of which at least oneis electrically connected to said first input conductor.
 16. Theapparatus of claim 10 further comprising a receiver integrated circuitchip having output signal processing circuitry therein that iselectrically interconnected to said first current sensor but otherwiseelectrically isolated from said current determiner including saidsubstrate thereof.
 17. The apparatus of claim 10 further comprising aninput converter integrated circuit chip having input signal processingcircuitry therein that is electrically interconnected to said firstinput conductor but otherwise electrically isolated from said currentdeterminer including said substrate thereof.
 18. The apparatus of claim12 wherein each of said first and second current sensors is electricallyconnected to a corresponding one of third and fourth current sensors,said third and fourth current sensors each being formed of a pluralityof magnetoresistive, anisotropic, ferromagnetic thin-film layers atleast two of which are separated from one another by a nonmagnetic layerpositioned therebetween, said fourth current sensor being electricallyconnected to said third current sensor, said first and third currentsensors being electrically connected in series with one another so as tobe suited for electrical interconnection across a source of electricalenergization and said second and fourth current sensors beingelectrically connected in series with one another so as to be suited forelectrical interconnection across a source of electrical energization toform a bridge circuit, said third and fourth current sensors supportedon said substrate adjacent to, yet spaced apart from, said first inputconductor to thereby be electrically isolated therefrom but positionedin those magnetic fields arising from said input currents.
 19. Theapparatus of claim 15 wherein said monolithic integrated circuitstructure in said substrate containing electronic circuit componentsalso has at least one of which that is electrically connected to saidsecond current sensor.
 20. The apparatus of claim 18 wherein said firstshield/concentrator layer is positioned near both said first inputconductor and said first and fourth current sensors, and furthercomprises a second shield/concentrator layer of material exhibiting asubstantial magnetic permeability that is positioned at that side ofsaid first input conductor facing said substrate but near both saidfirst input conductor and said second and third current sensors to serveas a magnetic field concentrator.
 21. The apparatus of claim 19 furthercomprising a second shield/concentrator layer of material exhibiting asubstantial magnetic permeability that is positioned at that side ofsaid second input conductor facing away from said substrate andelectrically connected thereto.
 22. A current determiner for providingat an output thereof representations of input currents provided thereinfrom a source of such currents, said current determiner comprising: asubstrate; a first current sensor supported on said substrate with saidcurrent sensor being formed of a plurality of magnetoresistive,anisotropic, ferromagnetic thin-film layers at least two of which areseparated from one another by a nonmagnetic layer positionedtherebetween; an input conductor supported on said substrate suited forconducting said input currents therethrough and positioned at that sideof said first current sensor opposite to that side thereof facing saidsubstrate so as to be adjacent to, yet spaced apart from, said firstcurrent sensor to thereby be electrically isolated from any directcircuit interconnection therewith on said substrate but to have saidfirst current sensor positioned in those magnetic fields arising fromsaid input currents in said input conductor; and a firstshield/concentrator layer of material exhibiting a substantial magneticpermeability to serve as a magnetic field concentrator and positioned atthat side of said second input conductor opposite to that side thereoffacing said substrate, said first shield/concentrator layer beingelectrically connected to said input conductor.
 23. The apparatus ofclaim 22 wherein said substrate further comprises a monolithicintegrated circuit structure containing electronic circuit components ofwhich at least one is electrically connected to said first currentsensor.
 24. The apparatus of claim 22 wherein one of said twoferromagnetic thin-film layers has a magnetization that is substantiallymaintained in a selected direction despite said magnetic fields arisingfrom said input currents causing reversals of direction of magnetizationof that remaining one of said two ferromagnetic thin-film layers. 25.The apparatus of claim 22 wherein said two ferromagnetic thin-filmlayers have magnetizations at least one of which changes in direction,due to magnetic fields arising from said input currents, with respect tothat direction thereof occurring due to a biasing electrical currenttherethrough absent any said input currents occurring in said firstinput conductor.
 26. The apparatus of claim 22 wherein one of said twoferromagnetic thin-film layers has a magnetization that is substantiallymaintained in a selected direction despite said magnetic fields arisingfrom said input currents causing changes in direction of magnetizationof that remaining one of said two ferromagnetic thin-film layers, andfurther including a third ferromagnetic thin-film layer spaced apartfrom that remaining one of said two ferromagnetic thin-film layers on aside thereof opposite that side across from which is positioned saidferromagnetic thin-film layer having a magnetization that issubstantially maintained in a selected direction.
 27. The apparatus ofclaim 22 further comprising a second current sensor supported on saidsubstrate adjacent to, yet spaced apart from, said input conductor tothereby be electrically isolated from any direct circuit interconnectiontherewith on said substrate but positioned in those magnetic fieldsarising from currents occurring in said input conductor, said secondcurrent sensor being formed of a plurality of magnetoresistive,anisotropic, ferromagnetic thin-film layers at least two of which areseparated from one another by a nonmagnetic layer positionedtherebetween.
 18. 28. The apparatus of claim 27 wherein each of saidfirst and second current sensors is electrically connected to acorresponding one of third and fourth current sensors, said third andfourth current sensors each being formed of a plurality ofmagnetoresistive, anisotropic, ferromagnetic thin-film layers at leasttwo of which are separated from one another by a nonmagnetic layerpositioned therebetween, said fourth current sensor being electricallyconnected to said third current sensor, said first and third currentsensors being electrically connected in series with one another so as tobe suited for electrical interconnection across a source of electricalenergization and said second and fourth current sensors beingelectrically connected in series with one another so as to be suited forelectrical interconnection across a source of electrical energization toform a bridge circuit, said third and fourth current sensors supportedon said substrate adjacent to, yet spaced apart from, said inputconductor to thereby be electrically isolated therefrom but positionedin those magnetic fields arising from said input currents.
 29. Theapparatus of claim 28 wherein said first shield/concentrator layer ispositioned near both said input conductor and said first and fourthcurrent sensors, and further comprises a second shield/concentratorlayer of material exhibiting a substantial magnetic permeability that ispositioned at that side of said input conductor facing away from saidsubstrate but near both said first input conductor and said second andthird current sensors to serve as a magnetic field concentrator, saidsecond shield/concentrator layer also being electrically connected tosaid input conductor.
 30. A monolithic integrated circuit containinginterconnected integrated circuit devices therein, said integratedcircuit comprising: a substrate containing an interconnected pluralityof integrated circuit devices with at least one interconnection theretoprovided at a support surface thereof; a shield/concentrator layersupported on said support surface of said substrate of materialexhibiting a substantial magnetic permeability to serve as a magneticfield concentrator; and a storage circuitry structure containing aninterconnected plurality of integrated circuit devices at least some ofwhich include therein thin-film layers of ferromagnetic material, saidstorage circuitry structure being positioned on portions of said supportsurface and on said shield/concentrator layer across from a plurality ofsaid integrated circuit devices including thin-film layers offerromagnetic material.
 31. A monolithic integrated circuit arrangementcontaining interconnected integrated circuit devices therein, saidintegrated circuit arrangement comprising: an integrated circuit chipcontaining an interconnected plurality of integrated circuit devices atleast some of which include therein thin-film layers of ferromagneticmaterial; and a support structure of material exhibiting a substantialmagnetic permeability to serve as a magnetic field concentratorsupporting said integrated circuit chip mounted thereon and havingelectrically isolated conductors provided therewith electricallyconnected to at least one interconnection extending from saidinterconnected plurality of integrated circuit devices.
 32. A monolithicintegrated circuit arrangement containing interconnected integratedcircuit devices therein, said integrated circuit arrangement comprising:an integrated circuit chip containing an interconnected plurality ofintegrated circuit devices at least some of which include thereinthin-film layers of ferromagnetic material; a support structuresupporting said integrated circuit chip and having electrically isolatedconductors provided therewith electrically connected to at least oneinterconnection extending from said interconnected plurality ofintegrated circuit devices; and a shield/concentrator layer attached tosaid support structure and of material exhibiting a substantial magneticpermeability to serve as a magnetic field concentrator.